1. Technological Field
This technical disclosure pertains generally to ultrasonic transducers, and more particularly to an ultrasonic transducer which can be readily configured for a desired dynamic response.
2. Background Discussion
Piezoelectric micromachined ultrasonic transducers (PMUTs) are micro-electro-mechanical system (MEMS) devices which operate in response to flexural motion of a thin membrane coupled with a thin piezoelectric film, instead of thickness-mode motion of a plate of piezoelectric ceramic as within bulk piezoelectric ultrasound transducers. It will be noted that PMUTs are a class of micromachined ultrasonic transducers (MUTs). In comparison with bulk piezoelectric ultrasound transducers, PMUTs can offer advantages such as increased bandwidth, flexible geometries, natural acoustic impedance match with water or air, reduced voltage requirements, mixing of different resonant frequencies and potential for integration with supporting electronic circuits especially for miniaturized high frequency applications.
However, despite the intensive study of MUTs in recent decades, most PMUT designs adhere to clamped square and circular plates, or if they have different mechanical configurations it is toward obtaining different goals/objectives than in this disclosure. For instance, certain PMUT configurations are targeted to achieve piston-like movement, in order to increase the output pressure and the active area of the device. Yet, piezoelectric actuated transducers require a curvature mode shape in order to couple the electrical and the mechanical energy efficiently. For example, a prior study performed by the inventors on a circular flexurally-suspended PMUT had a piston-like mode shape. It was found that although the linear operating range was increased, the output pressure and bandwidth were compromised.
Therefore, a need exists for enhanced PMUT designs which provide increased resonant frequency control, bandwidth and other enhanced operating characteristics.